One of the most important disturbances of roads is the facilitation of the increase of non-native invasive species into adjacent plant communities. The rupestrian fields of Serra do Cipo´, a montane grassland ecosystem in southeastern Brazil, are recognized for their enormous richness of species and endemism rates. The presence of non-native invasive species in this ecosystem could threaten the existence of the native flora and its associated organisms. The aim of this study is to understand how non-native invasive species and native species are distributed along paved and unpaved roads, in a montaneous grassland ecosystem such as the Brazilian rupestrian fields. The two road surfaces provide differing gradients from their edges with respect to nutrients, soil chemical aspects and plant species diversity. High content of calcium at the roadside in the paved road resulted from the paving process, in which limestone gravel is used in one of the several paving phases. In these newly created habitats the toxicity of aluminum is drastically reduced and nutrient enriched, hence representing favorable sites from where non-native invasive species are capable to colonize and grow for undetermined period waiting the chance to invade the adjacent pristine habitats. Disturbances provoked by any natural or humancaused event can provide the opportunity for the nonnative invasive species to colonize new plant communities.
We report on the insect galls on neotropical species of Baccharis (Asteraceae) and describe new kinds oi galls on Baccharis spp. of the cerrado and rupestrian fields of Brazil. Gall collections were made in several localities in Minas Gerais (Belo Horizonte, Caratinga; Lagoa Santa, Moeda, Ouro Preto, and Serra do Cip6). Baccharis may support the richest galling fauna of the neotropics (121 galling species on only 40 species of Baccharis). Nevertheless, gallers were not evenly distributed across host plant species. Four species of Baccharis alone supported 46% of the galling fauna. The most diverse fauna occurred on B. dracunculifolia (17 galls), B. concinna (15 galls), B. salicifolia (13 galls) and Baccharis sp.
To study the abundance and occurrence of herbivore insects on plants it is important to consider plant characteristics that may control the insects. In this study the following hypotheses were tested: (i) an increase of plant architecture increases species richness and abundance of gall-inducing insects and (ii) plant architecture increases gall survival and decreases parasitism. Two hundred and forty plants of Baccharis pseudomyriocephala Teodoro (Asteraceae) were sampled, estimating the number of shoots, branches and their biomass. Species richness and abundance of galling insects were estimated per module, and mortality of the galls was assessed. Plant architecture influenced positively species richness, abundance and survival of galls. However, mortality of galling insects by parasitoids was low (13.26%) and was not affected by plant architecture, thus suggesting that other plant characteristics (a bottom-up pressure) might influence gall-inducing insect communities more than parasitism (a top-down pressure). The opposite effect of herbivore insects on plant characteristics must also be considered, and such effects may only be assessed through manipulative experiments.
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